Want to build a Film Processor (basically a fancy waterbath)

[doigal]

Hey Guys,

I am thinking of building a film processor to automate some of the hassle of developing film. Essentially it needs to be a water bath that can hold 30 or 38°C (selectable depending on if its a slide or a negative. Also the better it can keep these temperatures the better, the E-6 spec calls for +/- 0.5°C but in practice it dosnt need to be that close), run a small motor for spinning the development tank and act as a timer for up to 10 different steps.

I can program a little bit and a very long time ago dabbled in some electronics but dont remember much of it at all. Basically before I start diving in, I just wanted a sanity check on if this plan might work.

Can an arduino hooked up to a waterproof thermometer, some form of LCD display with buttons, some form of water heater (advice on this would be great as well!), and a small buzzer work? Or do I need to be looking at some other form of controller?

It would be nice if it was all super integrated so that the one controller can take care of timing, temp control and spinning the film tank.

Any advice on this is welcome!

[paulvk]

"I can program a little bit " What language did you work with?

Regards Paul

[doigal]

mostly VBA and basic and a dabbling a little bit into some engineering programing (PCL). I have looked at the arduino stuff and it dosnt look that bad, and theres plenty of examples that can be cobbled together.

Its more the hardware stuff that I dont have much expirence in...

[zach]

Lots of threads on APUG/LFF about this sort of thing.

I think if you are going to bother building one, you'll want a lift to make changing the baths easier, you'll need a separate stepper motor & adruino board (if you go that route). I'm not an electrical engineer so can't really go into details on specs.

Adruino + thermocouple would be super easy temp control.

You could easily hack something together like this with some eskies - http://aussielargeformat.forumlaunch...c.php?f=5&t=78. I haven't spoken to Alex for a while but last I heard he was still working on it.

[doigal]

cheers for the link. Have been through APUG already and the project there seemed to fizzle out last i checked.

Hadnt seen the aussie large format thread, but I am reasonably sure that the aquarium heaters wont work unmodified - they will cut out before 38deg.

Would rather something that was all centrally controlled, the idea being its a one button press to change between the programs of C41 @ 30° and E6 @ 38°.

Anyone know of a 240v heater that would be good for this? This thread about a sous vide cooker here talks about the Norpro 559 but thats 110v only.

Initially I want to get the heating, rotation and timing down pat, and then worry about the mechanical bits of a lift, but yes the long term aim is to get it so that the only intervention you have to do is pour in the chemicals and it will do the rest for you.

[tumutbound]

This takes me back a bit

Many years ago, I used to service photo processing equipment (Wainco and Kreonite). No processing intelligence to speak of, all the timing was done mechanically.
The Wainco stuff was done via a lift mechanism that lifted the rolls of film between baths (Kodachrome process I think). The Kreonite was a more compact unit that used padded rollers to feed the film into different baths along the processing path.

Not a lot of help to you of course.

[zach]

Hahah sounds like a fun job tumutbound!

I'd imagine roller transport processors would be more difficult to build/maintain as opposed to a rotary. Plus some people get upset about rollers and emulsion being scratched.

Reviews say the Norpro takes 5-6 minutes to reach 100F, which is a loooong pre soak.

I'll keep a keen eye on this anyway, apologies for not being of any real assistance .

[doigal]

Originally Posted by zach

I'd imagine roller transport processors would be more difficult to build/maintain as opposed to a rotary. Plus some people get upset about rollers and emulsion being scratched.

Reviews say the Norpro takes 5-6 minutes to reach 100F, which is a loooong pre soak.

Roller or dip and dunk processors arent really for my kind of scale - I dont have the film volume to justify it, nor a true darkroom to store one! I wouldnt be using a roller transport one due to the risk of scratches like you say.

I dont presoak on colour devs, and the heater will be in the water bath not the actual development tank, so presoak time isnt a problem.

[RobRoySyd]

Originally Posted by zach

Adruino + thermocouple would be super easy temp control.

At these temperatures a RTD would be more suitable than a thermocouple.
For the heating element I'd consider the PTC heating elements from RS. They have the advantage that worst case they'll limit the temperature to some safe value. I've used them as the heating elements in a couple of drying ovens with considerable success.
In my application they were bolted to heatsinks with fans blowing over them. They'd be easily bolted to the outside of a water bath. In this application a number of smaller power units would ensure better heat distributiong into the liquid.
To stir the water a cheap cordless drill with a $2 paint stirrer in the chuck might do. Even an aquarium pump would work as the temps are not high.

[paulvk]

If you want to program an AVR and your background is in basic I reccomend Bascom AVR you can find it here http://www.mcselec.com/ and the free version does up to 4K of code which may be enough for what you want. It can program any AVR , it can use the Arduino boot loader. As its based on VB it is comfortable for people use , many of the functions you will want are commands in the language eg to print to an lcd or you do is LCD "Hello World"
There is an excellent very active forum here http://www.mcselec.com/index2.php?op...orum&Itemid=59 they will help you write the code , learn how to program and use the AVRs. Note it has no limits on the free verson other than not making more than 4K of code to go into the AVR and everybody gets treated the same on the forum.

Note with those heaters if you wire two in series you get 220V !

Regards Paul

[doigal]

An update to (hopefully!) prove this isnt just another case of vaporware. It works at the moment as a timer and temp monitor for a single film process. The hope is to integrate an immersion heater into it soon so the temperature control will be fully automatic.

Ignore the values, its just for testing!


Homebuilt Arduino Film Processor by doigal, on Flickr


Homebuilt Arduino Film Processor by doigal, on Flickr

The heater control isnt automatic at the moment, its just has an LED pin for when the temperature drops below a set point. I would like to move towards PID control as well rather than a simple if statement.

For reference, this is an arduino leo, LCD 4x20 screen controlled via I2C, a single button and a DS18B20 temperature probe (i got it pre-waterproofed from sparkfun).

Future work is to get some more testing in, theres a couple of bugs in the software that I would like to iron out before I release it to the wild. Then get the heater control done properly via a PID setup, a buzzer, keep working on the interface and move onto motorisation, lift, etc.